The production of nozzles in the form of perforated disks representing "S-type disks" is described in European Patent Application No. 0 354 660. According to this method, the inlet and outlet openings in the perforated disk are offset from one another, thus inevitably producing an "S pattern" in the flow of a fluid passing through the perforated disk. The proposed perforated disks are formed by two flat silicon wafers that are bonded together. Regions with a reduced thickness are provided on the silicon wafers so that shearing gaps are formed between the openings of the first wafer and the one opening of the second wafer parallel to the end faces of the wafers. The silicon wafers, which have a large number of perforated disk structures, are etched using known photomasking techniques, thus creating the inlet and outlet openings. The truncated tapered contours of the openings in the perforated disk logically result from the non-isotropic etching technique.
A fuel injection valve that has a nozzle composed of two silicon wafers on its downstream end is described in U.S. Pat. No. 4,907,748. As with the perforated disks described above, the inlet and outlet openings in the two silicon wafers are offset from one another, thus producing an "S pattern" in the flow of a fluid passing through the disk, which is fuel in this case.
In addition, perforated disks composed of two or three connected silicon wafers are described in German Patent Application No. 43 31 851. In this publication, an upper inlet opening in the upper wafer is followed by multiple outlet openings in the lower wafer with complete coverage. The perforated disks are provided for spraying a fuel-gas mixture with gas inflow channels from which a gas strikes the fuel to be sprayed largely perpendicularly.
All of the above-described perforated disks made of silicon have the disadvantage that they may not be sufficiently resistant to fracture because silicon is brittle. Especially when permanent loads are placed, e.g., on an injection valve (engine vibrations), there is the danger that the silicon wafers will break. Mounting the silicon wafers on metal components, such as injection valves, is complicated, since special stress-free clamping solutions must be found, and sealing the valve is problematic. It is not possible, for example, to weld the silicon perforated disks onto the injection valve. There is the further disadvantage of the edges of the openings in the silicon disks being worn away by the frequent passage of fluid.
The provision of a spray disk having multiple spray holes as well as an atomizer disk located further downstream is described in International Patent Publication No. 95/25889. The spray holes are provided in a central conical depression in the spray disk. This spray disk is followed by a completely separate atomizer disk, which is composed of multiple layers or wafers and into which air flows from the outside through a special opening geometry. The stainless steel wafers of the atomizer disk have an inner, central passage in which the air strikes, largely perpendicularly, the fuel emerging from the spray holes of the spray disk.